Myopia, or near sight,
is the condition where the range of focus of the eye is shortened,
making it unable to bring distant objects into focus. Some people
are genetically more predisposed to myopia than others. Having two
short-sighted parents will give a strong risk of developing myopia.
The way an individual uses their eyes, as well as their genes, will
determine how, or even if, they will become myopic. There are two
processes involved in the development of myopia: emmetropization,
which controls the growth of the rear of the eyeball and adult onset
myopia, which controls the stretching of the central part of the
eyeball.

Emmetropization:
Moving Towards Normal VisionWhile the eye grows, hormones control
the growth of the rear part of the eye. These growth hormones are
released in response to the degree of blur experienced when viewing
a distant object. If the distance is too sharp then the eye deems
itself too long sighted and growth is increased, lengthening the
eye and shortening the sight. If the distance is too blurred then
short sight is assumed and growth reduced at the back of the eye
while the rest of the eye continues to grow, thereby lengthening
the sight. This is called emmetropization, that is, seeking emmetropia,
or normal vision. While the eye is growing, up to around 14 years
old, it will tend to reduce refractive error (focusing problems)
provided it is seeing the world directly, without lenses. Unfortunately
this is rarely allowed to happen. The tendency has been for any
refractive error measured in a child to be ‘corrected’ using lenses.
The eye is then left to adapt to the world it sees through the lens,
dutifully changing its shape to cancel out the prescription within
a year or so. This results in stronger and stronger lenses being
prescribed and is called progressive myopia. This tendency can be
kept in check by allowing the eye to see the true distance (albeit
blurred), without glasses and out of doors, even for just one or
two hours a day.

Adult Onset Myopia To
bring near objects into focus the circular ciliary muscle contracts
allowing the lens to fatten providing the extra focusing power required.
The ciliary muscle has two parts: the circular fibres controlling
the lens and fibres that run along the eyeball itself spanning the
part of the eye between the ciliary body and the beginning of the
retina. These longitudinal fibres work in opposition to the circular
fibres so that when the circular fibres are relaxed for distant
focusing, the longitudinal fibres are tensed and when the circular
fibres are tense for close focusing, the longitudinal fibres are
relaxed. These longitudinal fibres have two functions: they help
to tense the suspensory ligament for distant focusing and they control
the elongation of the eyeball.The net result is that, in response
to prolonged close focusing, the eyeball lengthens, shortening the
sight. The eye gets better at the work it is used for. Unfortunately,
as it gets better at doing close work it may lose the ability to
focus the distance, creating myopia. This process is known as adult
onset myopia although it can happen at any age.Once glasses are
worn to bring the distance back into focus, the eye must work even
harder overcoming the prescription in order to focus close up. This
results in the myopia continuing to increase. This will happen to
anyone who continues to do a lot of close work through a distance
prescription.

What to do about myopia

There are various vision improvement systems for
reducing myopia which have a common theme; relaxation of the eyes
as well as the use of weaker than normal prescriptions. This makes
sense, as both will help the eyes to be more distance focused. Many
vision improvement practitioners now use Trayner pinhole glasses
alongside their traditional exercises. The artificially small pupil
provided by the Trayner Glasses encourages the eyes to focus beyond
their habitual range, giving a more active encouragement to distance
focus than is possible with the passive relaxation techniques.

Use Trayner pinhole glasses for at least half an
hour at the end of the day to focus further away than you normally
can (take out your lenses first). For some this will be reading,
for others watching TV. This will leave your eyes more distance
focused overnight. Avoid using your distance prescription for close
work. For students who alternate between looking at the blackboard
(distant) and their notebook (near), some opticians will now prescribe
bi-focals.